A feature of the coreless paper roll is that there is no core in the middle of the paper roll. A conventional rewinding machine utilizes a winding assisting plate to complete the start of the winding process during rewinding of such a paper roll. For example, according to a patent with Chinese patent NO. 94101338.3 and entitled “Improved rewinding machine for coreless winding of a log of web material with surface for supporting the log in the process of winding”, at the starting stage of rewinding, the disclosed rewinding machine makes a rewinding upper roller and a rewinding lower roller (called “winding rollers 1 and 3” in the patent) closed up temporarily, and depends on the support of a winding assisting plate (called “supporting surface 21” in the patent) to achieve the start of winding. After the start of winding, the rewinding upper roller and rewinding lower roller need to return to the normal position, so that the rewinding machine can continue rewinding. Such rewinding machine which depends on the winding assisting plate to perform the start of winding has the following defects:
1. the roller gap between the rewinding upper roller and rewinding lower roller has to be changed during the process from the start of winding to the rewinding, which causes the force applied on the paper roll to be not stable at the preliminary stage of rewinding, and thus easily causes failure of rewinding;
2. the winding assisting plate is used to support the paper roll at the preliminary stage of rewinding, which easily causes the force applied on the paper roll to be uneven. Thus, easily causes the tightness of the paper forming the core portion of the paper roll to be extremely uneven (known as “core portion wrinkling”), which seriously affects the subsequent process and the quality of finished products.
3. the rewinding lower roller moves while rotating at high speed, and the distance of movement must be precisely controlled, which certainly increase the structural complexity and manufacturing cost of the rewinding machine.
4. the front end of the winding assisting plate needs to be formed into comb shape and the tooth end of the comb is inserted into a ring groove which is provided on the cylindrical surface of the rewinding lower roller, and the ring groove provided on the cylindrical surface of the rewinding lower roller will leave significant indentations on the surface of the paper roll, which seriously affects the appearance of the paper roll.